Microstructure and properties of warm deformed 38Si7 spring steel for high-speed rail spring bars after heat treatment

doi:10.13251/j.issn.0254-6051.2023.11.017

Abstract

Abstract: For tested 38Si7 spring steel, the effect of warm deformation temperature on stress and microstructure, the effect of original microstructure on the microstructure and mechanical properties after quenching and tempering, and the effect of quenching and tempering parameters on the microstructure and mechanical properties were investigated, respectively, by means of optical microscope, scanning electron microscope, hardness tester and electronic universal testing machine. The results show that a higher deformation resistance is obtained when warm deformation temperature is between 720-800 ℃,which is 225.6-242.2 MPa. The temperature of warm deformation is selected as 800 ℃, at which the homogenization of microstructure of the 38Si7 spring steel is better. The main factor to control the content and morphology of retained ferrite is the quenching temperature. When the quenching temperature is higher than or equal to 880 ℃, the amount of retained ferrite in the microstructure of the 38Si7 spring steel can be greatly reduced. The strength and hardness of the steel increase with quenching temperature raising, while, its elongation decreases first and then increases. Quenched at 900 ℃, the 38Si7 spring steel has the best comprehensive mechanical properties, with tensile strength, hardness and elongation of 1396.8 MPa, 40 HRC, 12.5%, respectively, and the yield ratio is 0.9. The microstructure of network ferrite is presented when oil quenched, which is unfavorable to mechanical properties. When the tempering temperature is between 410-430 ℃, the effect of tempering temperature on microstructure and mechanical properties of the 38Si7 spring steel is slight. However, when the tempering temperature is 450 ℃, the strength and hardness are obviously reduced while the plasticity is improved. In conclusion, the optimal heat treatment process of the 38Si7 spring steel is 900 ℃×30 min, water quenching+430 ℃×60 min, air cooling.

Key words: 38Si7 spring steel, warm deformation, quenching, tempering, microstructure and properties

CLC Number:

TG156.1⁺3

Wang Tianjiao, Ding Xiaoming, Zhuang Qianyu, Jiang Bo. Microstructure and properties of warm deformed 38Si7 spring steel for high-speed rail spring bars after heat treatment[J]. Heat Treatment of Metals, 2023, 48(11): 112-119.

References

[1]史远, 黄艳新, 陈红卫, 等. 38Si7弹簧钢的奥氏体连续冷却转变规律[J]. 金属热处理, 2017, 42(5): 38-41.
Shi Yuan, Huang Yanxin, Chen Hongwei, et al. Austenite continuous cooling transformation of spring steel 38Si7[J]. Heat Treatment of Metals, 2017, 42(5): 38-41.
[2]付常林, 朱伟华. 38Si7钢的强韧化处理[J]. 山东冶金, 2000, 21(4): 36-38.
Fu Changlin, Zhu Weihua. Heat treatment of strengthening and toughening of 38Si7 steel[J]. Shandong Metallurgy, 2000, 21(4): 36-38.
[3]翟正龙, 李丰功, 杜显彬, 等. 铁路弹条用水淬弹簧钢38Si7的开发及应用[J]. 钢铁研究, 2001(4): 39-41.
Zhai Zhenglong, Li Fenggong, Du Xianbin, et al. Development and application of water quenched spring steel 38Si7 for railway spring fastener[J]. Research on Iron and Steel, 2001(4): 39-41.
[4]Lu Y, Xie H, Wang J, et al. Influence of hot compressive parameters on flow behaviour and microstructure evolution in a commercial medium carbon micro-alloyed spring steel[J]. Journal of Manufacturing Processes, 2020, 58: 1171-1181.
[5]韩治国, 严冉冉, 朱如峰. 高强度悬架簧用弹簧钢55SiCrA盘条轧钢生产实践[J]. 冶金与材料, 2021, 41(2): 11-12.
Han Zhiguo, Yan Ranran, Zhu Rufeng. Production practice of high strength spring steel 55SiCrA wire rod for suspension spring[J]. Metallurgy and Materials, 2021, 41(2): 11-12.
[6]屈小波, 谷杰, 侯兴辉. 60Si2MnA弹簧钢盘条开发实践[J]. 金属制品, 2017, 43(4): 23-28.
Qu Xiaobo, Gu Jie, Hou Xinghui. Development practice of 60Si2MnA spring steel wire rod[J]. Metal Products, 2017, 43(4): 23-28.
[7]孙宜强, 王成, 郑海涛, 等. 薄板坯连铸连轧弹簧钢60Si2Mn的组织和性能[J]. 金属热处理, 2018, 43(7): 139-143.
Sun Yiqiang, Wang Cheng, Zheng Haitao, et al. Microstructure and properties of spring steel 60Si2Mn produced by thin slab continuous casting and rolling process[J]. Heat Treatment of Metals, 2018, 43(7): 139-143.
[8]陈涛, 吴春京, 赵爱民, 等. 60Si2CrA的淬透性及低温回火温度对组织性能的影响[J]. 热加工工艺, 2016, 45(4): 196-198.
Chen Tao, Wu Chunjing, Zhao Aimin, et al. Effects of hardenability and low temperature tempering temperature on microstructures and properties of 60Si2CrA[J]. Hot Working Technology, 2016, 45(4): 196-198.
[9]孙萌, 姜周华, 李阳, 等. 汽车悬架用弹簧钢55SiCr制备技术的研究进展[J]. 中国冶金, 2022, 32(10): 25-37.
Sun Meng, Jiang Zhouhua, Li Yang, et al. Research progress for fabrication technology of automobile spring steel 55SiCr[J]. China Metallurgy, 2022, 32(10): 25-37.
[10]Podgornik B, Leskovšek V, Godec M, et al. Microstructure refinement and its effect on properties of spring steel[J]. Materials Science and Engineering A, 2014, 599: 81-86.
[11]王存宇, 周明博, 李晓东, 等. 温成形中锰钢的组织性能评价[J]. 钢铁, 2019, 54(10): 58-65.
Wang Cunyu, Zhou Mingbo, Li Xiaodong, et al. Evaluation of microstructure and properties of warm stamped medium manganese steel[J]. Iron and Steel, 2019, 54(10): 58-65.
[12]Wang X W, Hu Q H, Zhang C L, et al. Optimization of heat treatment for 38Si7 spring steel with excellent mechanical properties and controlled decarburization[J]. Materials, 2022, 15(11): 3763.
[13]李金波, 吴红艳, 高秀华, 等. 热处理工艺对高铁耐蚀60Si2Mn弹簧钢组织和性能的影响[J]. 金属热处理, 2022, 47(8): 135-140.
Li Jinbo, Wu Hongyan, Gao Xiuhua, et al. Influence of heat treatment process on microstructure and mechanical properties of corrosion resistant 60Si2Mn spring steel for high-speed railway[J]. Heat Treatment of Metals, 2022, 47(8): 135-140.
[14]崔娟, 刘雅政, 黄学启. 高品质60Si2MnA弹簧钢的热处理工艺优化[J]. 金属热处理, 2008, 33(6): 91-94.
Cui Juan, Liu Yazheng, Huang Xueqi. Heat treatment optimization of high quality 60Si20MnA spring steel[J]. Heat Treatment of Metals, 2008, 33(6): 91-94.
[15]潘广明, 卫广智, 朱海宁. 51SiCrV4弹簧钢热处理工艺的研究[J]. 现代机械, 2012(1): 74-76.
Pan Guangming, Wei Guangzhi, Zhu Haining. The study on heat treatment process of spring steel 51CrV4[J]. Modern Machinery, 2012(1): 74-76.
[16]黄文克, 王雷, 彭天兰, 等. 回火温度对弹簧钢55SiCrA组织与性能的影响[J]. 金属制品, 2011, 37(1): 61-64.
Huang Wenke, Wang Lei, Peng Tianlan, et al. Effect of tempering temperature on microstructure and properties of spring steel 55SiCrA[J]. Metal Products, 2011, 37(1): 61-64.
[17]吴华林, 王福明, 李长荣, 等. 提速列车用弹簧钢60Si2CrVAT的热处理工艺优化[J]. 材料热处理学报, 2011, 32(9): 35-41.
Wu Hualin, Wang Fuming, Li Changrong, et al. Optimization of heat treatment process of 60Si2CrVAT spring steel for high-speed trains[J]. Transactions of Materials and Heat Treatment, 2011, 32(9): 35-41.
[18]Huang S Q, Lu M, Luo S L, et al. Hot deformation characteristics and processing map analysis of pre-forged AZ80 magnesium alloy[J]. Metals and Materials International, 2021, 27(5): 1252-1262.
[19]王士付, 曹逻玮, 张峥. 14Cr1MoR钢珠光体球化研究[J]. 金属热处理, 2019, 44(S1): 553-555.
Wang Shifu, Cao Luowei, Zhang Zheng. Study on pearlite spherodization of 14Cr1MoR steel[J]. Heat Treatment of Metals, 2019, 44(S1): 553-555.
[20]杨跃辉. 两相区保温过程中9Ni钢组织的演化及其对钢性能的影响[J]. 热加工工艺, 2015, 44(22): 169-172, 175.
Yang Yuehui. Evolution of microstructure during holding process at two phase region and its effect on properties of 9Ni steel[J]. Hot Working Technology, 2015, 44(22): 169-172, 175.
[21]宫德海, 马永涛, 王小军, 等. 淬火温度对51CrV4弹簧钢组织及性能的影响[J]. 河北冶金, 2019(12): 20-23.
Gong Dehai, Ma Yongtao, Wang Xiaojun, et al. Effect of quenching temperature on structure and properties of 51CrV4 spring steel[J]. Hebei Metallurgy, 2019(12): 20-23.
[22]朱杰, 杨春林, 姜云, 等. 回火温度对60Si2CrVAT弹簧钢组织及性能的影响[J]. 金属热处理, 2016, 41(3): 54-57.
Zhu Jie, Yang Chunlin, Jiang Yun, et al. Influence of tempering temperature on microstructure and properties of 60Si2CrVAT spring steel[J]. Heat Treatment of Metals, 2016, 41(3): 54-57.
[23]许黎明, 陈银莉, 牛刚, 等. 回火温度对Si-Mn系中碳弹簧钢组织及性能的影响[J]. 轧钢, 2016, 33(3): 29-32.
Xu Liming, Chen Yinli, Niu Gang, et al. Influence of tempering temperature on mechanical properties and microstructure of Si-Mn medium carbon spring steel[J]. Steel Rolling, 2016, 33(3): 29-32.
[24]姜婷, 汪开忠, 于同仁, 等. 热处理工艺对弹簧钢55SiCrV力学性能和组织的影响[J]. 金属热处理, 2019, 44(10): 96-99.
Jiang Ting, Wang Kaizhong, Yu Tongren, et al. Effect of heat treatment process on mechanical properties and microstructure of 55SiCrV spring steel[J]. Heat Treatment of Metals, 2019, 44(10): 96-99.